Diamond relay network under Rayleigh fading: On-off power control and outage-capacity bound

The achievable outage probability of the diamond relay network under Rayleigh fading is investigated. Two existing transmission protocols are considered, namely, the Alamouti-Coded Amplify-and-Forward (ACAF) and the Alamouti-Coded Decode-and-Forward (ACDF). For ACAF, a distributed optimal power control rule for the two relays is analytically derived. Simulation results show that with this power control rule, the diversity gain of ACAF increases from one to two, and its performance approaches that of ACDF in the high signal-to-noise ratio (SNR) regime. For ACDF, a performance bound is analytically obtained: for any outage probability e, its SNR offset is bounded above by 3 dB and its e-outage rate is within 1 bit of the e-outage capacity of the diamond relay network.